Threaded fasteners such as bolts and screws are widely used in nearly every application to secure machine parts and the like by engaging corresponding threads on a nut or work piece. These bolts and screws are commonly provided with a polygonal head portion having a series of flat surfaces with well defined corners aligned generally parallel to the axis of the threaded portion of the fastener. The head is usually hexagonal in shape, although bolts having square or other polygonal shapes are sometimes found. The polygonal head portion usually has one of a plurality of standard sizes, measured either in metric or English dimensions, so that the head may be engaged by standard size tools. A variety of tools are commonly used to engage fastener heads, including closed and open end wrenches and sockets driven by a wrench or driver portion. Fastener nuts are also typically polygonal, and may also be engaged by these tools, and any future reference to fastener heads or bolt heads will also be understood to include nuts.
A socket for turning a fastener head generally has a body portion made of a durable material such as hardened steel or the like within which a polygonal receptacle is defined. The polygonal receptacle of the socket has a size appropriate to fit a corresponding standard size head. Sockets generally provide good performance when engaging heads that are in like new condition and on which the polygonal surfaces and corners have not deteriorated. However, after repeated use, a fastener head sometimes becomes deformed, thus impeding the efficacy of a conventional socket wrench as well as other conventional tools.
The most common type of deformation occurring on a fastener head is rounding of the corners on the head. A rounded-off head, which is sometimes referred to as a stripped bolt head, may result from slippage of a wrench, socket or other tool about the fastener head when turning the fastener. Use of an improper tool or wrong size tool to turn the fastener may also damage the head surfaces. The rounded head frequently develops while attempting to turn a fastener that is very tight, or which is corrosively adhered to a surface, work piece or nut. In such situations, conventional sockets and other tools fail to provide adequate turning power and slip around the fastener head, causing damage to the head.
In the past, attempts to turn fasteners having rounded or stripped heads have enjoyed varying degrees of success. Locking pliers are often used to clamp tightly on the deformed head to turn it. The use of locking pliers, however, often causes further deformation of the head and may even destroy the head so that the fastener is no longer serviceable. For example, if the pliers are not sufficiently tight, they will slip around the head when a torque is applied. Alternatively, if the locking pliers are applied tight enough to remove a stubborn fastener, the head may be permanently deformed due to compression by the plier jaws.
A particularly problematic situation arises when a deformed fastener head is positioned within a small recessed area. Such recessed areas are frequently found on machine parts, engines and other applications where it is desirable that the fastener head not protrude above an otherwise flush surface. The recessed area for a fastener head is typically only slightly larger in diameter than the size of the fastener head, allowing only enough room for a socket to extend into the recess and engage the fastener head. This arrangement is quite acceptable when the fastener head has well defined surfaces; however, if the fastener head has become rounded or otherwise deformed, locking pliers or other known tools cannot extend into the recessed area to grasp the bolt head such that an adequate torque can be generated to turn the fastener.
Other especially designed tools are available which clamp tightly on a deteriorated fastener head or which cut into the fastener head, but these tools are also frequently destructive, rendering the fastener permanently unserviceable, or are incapable of engaging a fastener head within tightly constricted areas, or both. For example, U.S. Pat. No. 4,920,834, which issued to Womack et al. on May 1, 1990 shows a socket pipe wrench having an adjustable sliding jaw therein for turning a nut or bolt having a mutilated head. However, the tool shown in the Womack et al '834 patent cannot engage fastener heads within tightly constricted areas due to its relative bulk, and the jaw teeth may cause further damage to a deformed fastener head received therein. Likewise, U.S. Pat. No. 2,746,328, which issued to Valvano on May 22, 1956, shows a tool having wedge-like moveable jaws. However, this tool is especially adapted for removing a stud bolt lacking a polygonal head.
Another stud bolt puller is shown in U.S. Pat. No. 3,094,022, issued to Young on Jun. 18, 1963. The Young '022 stud puller has a plurality of bolts aligned transverse to the axis of the stud puller which may be adjusted to engage the stud. This tool, however, is not adapted for turning polygonal fastener heads as it has a circular interior bore. Last, French Patent No 608,191, issued to Bernard and published Jul. 22, 1926, shows a wing-nut adapter which has a socket for engaging the hexagonal head of a spark plug. A screw penetrates one vertex of the socket and may be adjusted to retain the adapter on the head; however, the adapter cannot securely engage a deformed head.